In an ink-jet printer, an ink-jet head distributes ink supplied from an ink tank to pressure chambers. The ink-jet head selectively applies pulsed pressure to each pressure chamber to eject ink through a nozzle. As a means for selectively applying pressure to the pressure chambers, an actuator unit having laminated ceramic piezoelectric sheets may be used.
As an example, a generally-known ink-jet head has one actuator unit in which continuous flat piezoelectric sheets extending over a plurality of pressure chambers are laminated. At least one of the piezoelectric sheets is sandwiched by a common electrode and many individual electrodes, i.e., driving electrodes. The common electrode is common to the pressure chambers and is kept at the ground potential. The many individual electrodes, i.e., driving electrodes, are disposed at positions corresponding to the respective pressure chambers.
The part of piezoelectric sheet being sandwiched by the individual and common electrodes, and which is polarized in its thickness, acts, by applying an external electric field, as an active layer that deforms by piezoelectric effect. Therefore, when an individual electrode on one face of the sheet is set at a different potential from the potential of the common electrode on the other face, the active layers are expanded or contracted in its thickness direction by the so-called longitudinal piezoelectric effect. The volume of the corresponding pressure chamber thereby changes, so ink can be ejected toward a print medium through a nozzle communicating with the pressure chamber.
In the above-described ink-jet head, however, the individual electrodes are arranged on the plurality of laminated piezoelectric sheets. Accordingly, in order to manufacture this ink-jet head, a series of complicated steps are required to form through holes for connecting individual electrodes located at positions overlapping in a plan view, and burying a conductive material in the through holes.
Therefore, a primal objective of the invention is to provide an ink-jet head which does not require to form through holes for feeding driving signals to the individual electrodes in piezoelectric sheets, thereby improving its manufacturing process.